Worn radius arm bushings let the front axle wander fore and aft under acceleration and braking — you'll feel it as a clunk on throttle-off or vague steering at highway speed. Energy Suspension 4.7110R is the standard polyurethane kit; rubber Moog bushings work for daily drivers that want a softer ride.
The Full-Size Bronco's TTB front axle locates each beam fore-and-aft with a long radius arm running back to a frame mount. The radius arm bolts to the beam at the front and threads through a rubber bushing at the rear frame mount. That rear bushing takes every acceleration and braking force the front axle generates — the entire chassis pulls against it under acceleration, and the truck's mass pushes against it under braking. Rubber bushings collapse, crack, and eventually delaminate. The first symptom is a clunk when you transition between gas and brake.
Replacing the bushings tightens up the front end dramatically. A 25-year-old truck with original rubber bushings feels like the front axle is mounted to the frame by spaghetti. New bushings make it feel like a different vehicle.
Two material choices: polyurethane and rubber. Polyurethane (Energy Suspension 4.7110R) lasts substantially longer than rubber, transmits more road noise and vibration to the cabin, and locates the axle more rigidly under load. Rubber (Moog or OEM equivalent) rides softer and is quieter, but wears faster and lets more axle movement through. For a daily driver Bronco that sees pavement, rubber is fine. For a trail truck or a truck running larger tires, polyurethane is the better fit.
The color of the polyurethane (red vs. black) is purely aesthetic. Energy Suspension catalogs both. Pick whichever you like; the durometer (hardness) is identical.
The job itself is straightforward in concept and miserable in execution if the bushings have been in place for 25 years. The retaining nut at the rear of the radius arm is tight, exposed to road salt and grit, and torqued to 220+ ft-lb from the factory. Plan for a breaker bar, an impact gun, or a torch.
Lubricate polyurethane bushings on install with the included grease (silicone-based — *do not* use petroleum-based grease on polyurethane, it eats the material). Re-grease every 50,000 miles if you start hearing a squeak from the front end.
| Part | Vendor | Est. price |
|---|---|---|
| Energy Suspension radius arm bushing kit (polyurethane) | Energy Suspension | ~$45 |
| OEM-style rubber radius arm bushings | Moog / Daystar | ~$35 |
| Radius arm nut + retaining washer kit | Dorman | ~$15 |
| Black polyurethane (alternative color) | Energy Suspension | ~$45 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.